含氮不锈钢凝固模式及显微组织研究

研究了四种不同N含量的18Mn18Cr N不锈钢的凝固模式、显微组织和元素分布.结果表明:N含量影响18Mn18Cr N合金系的凝固模式和显微组织.氮的质量分数由0.07%增加至0.72%时，实验钢的凝固模式由F模式转变为A模式，显微组织由铁素体和奥氏体魏氏两相组织转变为铁素体和奥氏体两相组织以及单相奥氏体组织.N含量影响奥氏体相形貌，随N含量增加，奥氏体由板条状、针状转变为枝晶间和等轴状.枝晶间和等轴状奥氏体晶粒中存在褶皱形貌，且随着氮含量增加，褶皱数量增多.褶皱的产生与凝固过程中奥氏体相内部Fe、Mn、Cr元素的偏析有关，且该凝固偏析被保留至室温组织中. 

Solidification mode and microstructure of nitrogenous stainless steels

This article reports the solidification mode, microstructure, and element distribution of phases in 18Mn18CrN stainless steels with four kinds of N contents. N content significantly affects the solidification mode and microstructure of 18Mn18CrN alloy systems. The solidification mode of 18Mn18CrN stainless steels changes from Mode F to A as the N content increases from 0.07% to 0.72%. Additionally, the microstructure of 18Mn18CrN stainless steels changes from ferrite + austenite Widmanstätten dual-phase structure to ferrite + austenite dual-phase structure and a single phase of austenite as the N content increases. N content also affects the morphologies of austenitic phases. The lath-like or needle-like austenite phase changes into interdendritic and equiaxed austenite phases with the increase of N content. Ridges are present in interdendritic and equiaxed austenite grains, and the amount of ridges increases as the N content increases. There is a relationship between the ridges and the segregation of Cr, Mn and Fe elements in austenite phases during the solidification process. Moreover, this solidification segregation is retained to room temperature microstructure.